1. Field of the Invention
This invention relates to an electroluminescent device, particularly to an electroluminescent device which emits light through recombination of carriers injected or excited by the energy of light or electrical field.
2. Related Background Art
Conventionally, electroluminescent devices utilizing electroluminescent phenomenon of semiconductors may be classified broadly into those utilizing the injection electroluminescent effect and those utilizing the electrical field electroluminescent effect. As the semiconductor material to be used, combinations of III-V group elements such as GaAs, Ga-Al-As, etc. or combinations of II-VI group elements such as ZnSe, ZnS, etc. may be used, and the band gap or the excitation level can be changed by changing the compositional ratio of the matrix material or changing the impurity introduced into the matrix material, whereby the emitted light wavelength can be changed. On the other hand, as to the structure of the device, in most cases, a PN junction, a PIN junction, a hetero junction, a Schottky junction, etc. is constructed by use of a single crystal. When a color display is designed to be constituted by arrangement of such electroluminescent devices, devices emitting three primary colors will be combined. Accordingly, it is necessary to select materials while taking the lattice constant and the band gap of the crystal corresponding to the respective colors. Also, since the number of the elements becomes so large, the mounting density is not so high, and there is also involved the problem of low resolution.